Always use an air conditioner that’s correctly sized for your home. An oversize unit may cycle on and off too quickly, making it ineffective at removing humidity and maintaining uniform temperatures. On the other hand, a too-small unit will need to run constantly, which will drastically shorten its lifespan. Determine your needed cooling capacity by doing a load calculation, taking into account each room’s square footage, layout, insulation, function, and typical occupancy. To learn more, download this worksheet from the Energy Star website, or consult an air-conditioning contractor.

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Because cooling an empty house wastes both money and energy, upgrade to a programmable thermostat. This technology allows you to raise and lower the temperature of your AC based on a preset schedule, which can save hundreds of dollars annually. Boost your energy efficiency even more by closing vents in unoccupied rooms as well as keeping closet and cabinet doors shut so excess air doesn’t get in.

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Although air conditioners aren’t the most attractive items in a landscape, homeowners shouldn’t try to “hide” their unit in an inopportune spot. The location of an air conditioner has a big impact on its energy efficiency. Try installing it in a shady spot on the east or north side of your house, because too much direct sunlight will make the system work harder. Additionally, don’t place concealing shrubs or plants too close to the unit, as these will impede ventilation and may clog the condenser coils.

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Inside your home, make sure the thermostat and vents are properly positioned. Placing the thermostat in direct sunlight or near heat-producing lights and appliances gives an inaccurate reading, causing the air conditioner to work overtime. Also, blocking interior vents with furniture or curtains may inhibit proper air circulation.

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Many homeowners feel content with temperatures in the high 70s but set their thermostat much lower out of habit. Adjusting to a higher setting will save you big bucks on utility bills; in fact, you can cut 3 percent off your AC costs for every degree you raise the temperature. 

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If possible, combine your air conditioning with the use of strategically placed fans. Any type of fan helps cool the air circulating throughout your home, which will make you feel more comfortable at a higher indoor temperature. Be sure to set ceiling fans to run counterclockwise during the summer in order to push the air downward. Note that you should also minimize the use of exhaust fans in the kitchen and bathroom while you're running the AC, as these remove cool air from your home.

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Open doors and windows invite humidity inside your home and let chilled air escape. Your air conditioner must then work extra hard to compensate, wasting vast amounts of energy along the way. Always keep doors and windows closed when the AC is running. 

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Clean or replace air filters every month during the cooling season, and more frequently if the filter seems excessively clogged with dust and debris. A clean filter significantly improves an air conditioner’s efficiency, lowering your energy consumption by 5 to 15 percent. On central air conditioners, filters are typically located on the return ducts in walls or ceilings. Room air conditioners have a filter mounted in the front-facing grille, while ductless mini-splits store their reusable filter in a removable panel. Consult your owner’s manual for exact instructions on changing the air filter.

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Outdoor condenser and evaporator coils can become clogged with dirt, which blocks airflow and insulates the coils, reducing their ability to manage heat efficiently. To keep the coils from clogging, don’t place your AC components near dryer vents, and remove fallen leaves, grass clippings, and other outdoor debris regularly. Trim shrubs and other foliage to give at least two feet of space around the condenser, allowing for adequate airflow.

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Properly maintaining your air-conditioning equipment will maximize its operating efficiency and effective lifespan. At the beginning of the cooling season, inspect the seals on the air conditioner as well as the seals between the unit and the house to ensure no cool air is escaping. Then, check the fuses, circuit breakers, wire, and terminals for corrosion; evaluate the condensate drain for proper drainage; and examine fans and other moving parts for signs of wear.

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Some problems with air-conditioning systems, such as refrigerant leaks, can be diagnosed and repaired only by a qualified HVAC technician. Have a professional give your system an inspection and tune-up on a regular basis. Remember: A routine service call is most likely going to be far cheaper than an emergency repair!

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